1. Field of the Invention
The present invention relates to a COG (Chip On Glass) type liquid crystal display panel, particularly to a liquid crystal display panel upon which intermediate functional inspection can be conducted before mounting an IC (Integrated Circuit) chip for driving liquid crystal.
2. Background Art
The COG type liquid crystal display panel is so constructed that the chip mounting area for mounting the IC chip to drive the liquid crystal is provided on one of a pair of substrates on which a plurality of electrodes are formed in a matrix state, whose peripheral areas are bonded together by a sealing material, between which liquid crystal is filled, a plurality of extraction electrodes severally connected to the electrodes are lead out to the mounting area, and terminals for bump, which are connected to bump terminals of the IC chip that drives the liquid crystal, are formed on these lead out extraction electrodes.
Subsequently, before mounting the IC chip for driving liquid crystal on the substrate, an intermediate functional inspection is performed for such faults as the presence of broken electrodes, short circuit between electrodes and whether or not the display performs as designed when a predetermined voltage is applied to the electrodes. The inspection method is performed by allowing contact pins to contact the tip portions of the plurality of electrodes and applying voltage to each electrode through the contact pins.
Such inspection method can be executed without a problem when gaps between the plurality of electrodes are wide. However, liquid crystal display panels of cell phones or the like have become higher definition and gaps between electrodes have accordingly become narrower, and on the other hand, circuit design is such that a large number of extraction electrodes concentrate on the chip mounting area. Therefore, allowing the contact pins to contact each electrode has become a very difficult task.
As a method of getting round this difficult task, an inspection is performed in which predetermined terminals of the plurality of terminals for bump are selected, that is, every other terminal for bump is selected for example, and the contact pins are allowed to contact them.
However, this method also requires high accuracy in aligning the contact pins. In addition, its work efficiency is poor, working time increases proportionally with an increased number of terminals for bump and IC chips, and thus inspection errors easily occur. Further, there is a danger that the terminals for bump will be damaged because the contact pins are allowed to contact the terminals for bump.
In fact, to solve such inconvenience, a liquid crystal display panel is known in which, in addition to the terminals for bump, terminals for inspection are provided to make substrate inspection before mounting the chip for driving the liquid crystal easier (See Japanese Patent Laid-Open No. 2000-137239 Publication (FIG. 3, paragraphs [0017] to [0022]), for example).
FIG. 8 is an enlarged plan view of a principal portion of the liquid crystal display panel described in the above Japanese Patent Laid-Open No. 2000-137239.
The liquid crystal display panel 80 includes a front glass substrate 81 and a rear glass substrate 82 with a slightly larger area than the substrate 81, and it has a construction such that liquid crystal is filled in the area formed by the facing substrates 81, 82 via a peripheral sealing material 83 to form a display region, a chip mounting area MA on which the IC chip for driving liquid crystal (not shown) is mounted is provided on a projected portion of the rear glass substrate 82, and the end portion of each extraction electrode 84 is extended into the chip mounting area MA.
In each extraction electrode (84a to 84i), an area with a predetermined length in the chip mounting area MA is used as a bump connection area A for connection to the bumps of an IC chip. In each bump connection area A of each extraction electrode 84a to 84i, an extended area B extending in the opposite direction to the peripheral sealing material 83, that is, extending further into the chip mounting area MA is provided repeatedly, and a square-shaped broadened land R, which is wider than the width of the bump connection area A is severally formed on the terminal portion of each extended area B.
Each extended area B has a different length, with the extended areas B of odd numbered extraction electrodes 84a, 84c, 84e, 84g, and 84i being short, and the extended areas B of even numbered extraction electrodes 84b, 84d, 84f, and 84h having a length exceeding the odd numbered broaden lands R.
Therefore, when the broadened land R is formed on the terminal portion of each extraction electrode 84a to 84i, in the case where inspection is performed by a pin probe method before mounting the IC chip 84, the contact pins are able to contact the broadened land R due to its width as shown in the black circles in FIG. 8, so that strict alignment accuracy is unnecessary and the inspection becomes easier in comparison to the conventional case in which the contact pins are allowed to contact the bump connection areas A.
However, in the above-described Japanese Patent Laid-Open No. 2000-137239, since each broadend land R must be made wider than the width of the bump connection area A, which is in a square shaped broadened land for example, they can not be housed in the chip mounting area when the number of lands is increased. Liquid crystal display panels in recent years have a large number of electrodes and they are arrayed in high density, so that a large number of such broadened lands cannot be arranged within the chip mounting area.
Furthermore, regarding the inspection method, because the contact pin must individually contact each land, the work efficiency of inspection is poor and the working time is increased. Additionally, if inspection is performed by allowing all of the contact pins to contact the terminals for bump, a very expensive inspection device will be necessary. Still further, when a simple inspection device using conductive rubber is used in the case where positions for arranging different types of terminals (for source electrodes, for gate electrodes, for common electrodes) are not divided, terminals that are not intended to be turned on are turned on if the different types of terminals are arranged adjacent to each other, and inspection cannot be performed properly.
Consequently, the present inventors have developed a liquid crystal display panel to solve the above-described problems, in which terminals for inspection are additionally extended from the terminals for bump into the chip mounting area, terminals for inspection, which are extended from one type of terminal for bump, out of the terminals are arranged in a row, and different types of terminals can be inspected simultaneously by using conductive rubber to improve workability, and have already applied for patent for this invention as Patent Application No. 2004-181474 (hereinafter, referred to as prior application).
FIG. 9 is an enlarged plan view showing the chip mounting area and the surrounding of the liquid crystal display panel of the prior application.
In the liquid crystal display panel of the prior application, extraction electrodes 120, which are connected to a plurality of electrodes arranged in a matrix state, are wired so as to concentrate in the chip mounting area MA, terminals for bump 121a to 121n are positioned in the chip mounting area MA, and terminals for inspection 122a to 122n are positioned so as to form a line by and alongside the terminals for R, G and B via the extraction electrodes from the terminals for bump 121a to 121n, as shown in FIG. 9.
An inspection probe (not shown) made of a belt-shaped conductive rubber is allowed to contact the terminals for inspection 122a to 122n that are positioned in this manner, and thus intermediate functional inspection can be achieved collectively according to the type of each terminal for bump 121a to 121n. 
However, in the above-described prior art, inspection can be performed accurately and the number of inspections can be drastically reduced when terminals are provided on one side (a) out of four sides (a) to (d) of a rectangular chip mounting area MA, and there are panels which have a fairly large number of extraction electrodes 120 with the demand for higher definition from liquid crystal display panels in recent years. Regarding such panels, it is necessary for extraction electrodes to be drawn around to each side (three sides (a), (c), (d), for example) of the chip mounting area MA. In this case, since it is not only necessary to perform intermediate functional inspection of each of the terminals for inspection, which are positioned on each side, but also the terminals for inspection concentrated in the central area of the chip mounting area MA, there has been a danger that inspection could not be performed accurately when using the conductive rubber.